• Title/Summary/Keyword: 비틀림 실험

Search Result 216, Processing Time 0.023 seconds

Torsional Strength and Failure Modes of Reinforced Concrete Beams Subjected to Pure Torsion (순수비틀림을 받는 철근콘크리트 보의 비틀림 강도와 파괴모드)

  • Lee, Jung-Yoon;Kim, Sang-Woo;Kim, Ji-Hyun
    • Journal of the Korea Concrete Institute
    • /
    • v.20 no.4
    • /
    • pp.503-511
    • /
    • 2008
  • This paper presents the results of an analytical and experimental study on the performance of reinforced concrete beams subjected to pure torsion. The main parameters of the experimental tests were amount of torsional reinforcement and the ratio of the transverse torsional reinforcement to the longitudinal torsional reinforcement. The test results indicated that the maximum amount of torsional reinforcement required in ACI 318-05 code underestimated almost twice as much as the observed maximum amount of torsional reinforcement. Comparisons between the tested and calculated torsional behaviors of the 102 beams showed that the torsional failure modes of ACI 318-05 code disagreed with the observed failure modes. In addition, the torsion provisions in ACI 318-05 code overestimate the torsional strength of the RC beams in which relatively large amount of torsional reinforcement were reinforced, while underestimate for the beams with small amount of torsional reinforcement. This discrepancy between the theoretical ultimate torsional strength as given by the ACI 318-05 code and the experimental one can be due to neglecting the tension stiffening effect and the contribution of the torsional strength by concrete.

A Stdy on Clutch-disc Torsional Characteristics for Torsional Vibration Reduction at Idling (공회전시 비틀림 진동 저감을 위한 클러치 비틀림 특성 연구)

  • 홍동표;정태진;김상수;태신호
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 1994.04a
    • /
    • pp.82-87
    • /
    • 1994
  • 자동차 엔진의 주기적인 연소과정 동아네 생성된 힘에 의해 엔진의 크랭크 샤프트에 회전 불균일성이 나타난다. 이것은 엔진 플라이휘일 부분에 비틀림 변동토크를 발생시키고, 이 토크는 클러치를 통하여 변속기의 인풋기어(input gear)에 전달되어 변속기에 비틀림 진동을 일으키는 주요 원인이 된다. 공회전시 변속기에서 기어의 충돌은 주로 이 비틀림 변동토크에 의해 발생하며, 이 충돌은 차내 소음의 원인이 된다. 또한 엔진의 경량화 및 고출력화에 따른 회전수 변동의 증가는 비틀림 변동토크를 증가시켜 변속기에 커다란 진동을 초래한다. 시뮬레이션을 사용한 클러치 비틀림 기구의 적절한 특성치를 구하는 것은 클러치 설계에 효율적이고, 이미 여러 연구 결과들이 보고되었다. H.Arai은 2자유도 비선형 모델을 사용하여 클러치 접속시 발생하는 외란과 계의 안정성을 고려하여 치타음 저감을 위한 시뮬레이션을 수행하였고, S.Ohnuma은 비선형 2단 비틀림 특성을 가진 클러치 디스크의 설계에 대해서, 그리고, T.Fujimoto와 R.J.Comparin는 치타음의 발생구조와 특성을 고찰하고 비선형 비틀림 공진 저감에 의한 치타음 저감 기법에 대하여 연구하였다. 그리고, Wu Hui-Le는 자동차 동력전달계의 비틀림 진동 현상을 실험과 이론적인 계산을 통해 연구하였고, G.J.Fudala는 다자유도 모델을 이용하여 클러치의 비틀림 특성에 따라 주파수분석을 수행하여 치타음 저감 방법을 연구하였다. 또한, T.Sakai는 5자유도 모델을 이용하여 엔진 공회전시 발생하는 치타음에 대해 이론과 실험을 통해 해석하고, 엔진 회전수 변동, 클러치 특성, 변속기의 드래그(drag) 토크의 영향과 치타음 저감을 위한 개선된 클러치 특성을 제시하였다. 클러치는 동력을 전달 또는 차단하는 기능 뿐만 아니라 엔진이나 변속기에서 발생하는 소음이나 진동을 저감시키는 기능을 가지고 있다. 따라서 엔진 공회전시에 발생하는 치타음(rattle noise)이나 비틀림 진동을 저감시키는 방법으로는 여러가지가 있으나 클러치 디스크(clutch disc)의 비틀림 기구의 설계 인자들을 적절히 조절함으로써 변속기의 인풋기어에 전달되는 비틀림 진동을 저감시키는 방법이 일반적으로 수행되어지고 있다. 본 연구는 4 실린더 4 싸이클 1.5L 엔진을 장착한 경승용차의 실차실험을 통해 공회전시 엔진 플라이휘일과 인풋기어에서의 회전수 변동을 측정하고, 이 실험 데이타를 기초로 하여 엔진 토크 및 변속기에서의 드래그 토크를 계산하여 엔진-변속기 인풋기어의 반한정계 2자유도 진동모델과 비틀림 특성을 가진 클러치 디스크의 프리댐퍼 영역에 대해 시뮬레이션을 수행하여 클러치 비틀림 기구의 설계인자인 비틀림 강성, 히스테리시스 토크에 따른 비틀림 진동 저감 효과를 연구하고자 한다.

  • PDF

Prediction of the Torsional Strength of Reinforced Concrete Beams Subjected to Pure Torsion (순수비틀림을 받는 철근콘크리트 보의 비틀림 강도 예측)

  • 이정윤;박지선
    • Journal of the Korea Concrete Institute
    • /
    • v.14 no.6
    • /
    • pp.1010-1021
    • /
    • 2002
  • The current ACI design code does not take into account the contribution of concrete for the torsional moment of reinforced concrete(RC) beams subjected to pure torsion. This code is not capable of evaluating the inter-effects between concrete and torsional reinforcement on the torsional resistance of the RC beams. Some test results indicated that the current ACI code was not successful in predicting the observed torsional moment of the RC beams with reasonable accuracy. The research reported in this paper provides an evaluation equation to predict the torsional moment of the RC beams subjected to pure torsion. The proposed equation is derived from the equilibrium as well as compatibility equations of the truss model for the cracked RC beams. Comparisons between the observed and calculated torsional moments of the 66 tested beams, showed reasonable agreement.

Torsional vibration of engine crank shaft (엔진 크랭크 축계의 비틀림 진동)

  • 강구태;여승동
    • Journal of the korean Society of Automotive Engineers
    • /
    • v.10 no.5
    • /
    • pp.9-16
    • /
    • 1988
  • 엔진 크랭크축계의 비틀림진동은 엔진설계 및 제작에 있어서 오랜동안 주관심사였다. 크랭크축계의 비틀림진동에서 고려되는 문제는 비틀림진동계의 고유진동수와 이에 따른 차수별 엔진의 공진속도와 엔진의 공진속도에서의 비틀림진동각 및 크랭크축의 비틀림진동에 의한 토오크와 비틀림 응력 등이다. 당사에서는 simulation program을 개발했으며, 비틀림 진동측정 방법도 개발했다. 또한 비틀림진동 측정결과와 simulation결과의 비교로부터 simulation결과 및 측정결과의 정확도를 높여가고 있으며, simulation 방법의 개선을 모색하고 있다. 본 글에서는 이 program에 이용된 기본이론과 실험방법 및 댐퍼 선정 방법을 간단히 소개하고자 한다.

  • PDF

Characteristics of Structural Behavior of Steel Fiber Reinforced Ultra High Performance Concrete Beams Subjected to Torsion (강섬유 보강 초고성능 콘크리트 보의 비틀림 거동 특성)

  • Yang, In-Hwan;Joh, Changbin;Lee, Jung-Woo;Kim, Byung-Suk
    • Journal of the Korea Concrete Institute
    • /
    • v.26 no.1
    • /
    • pp.87-95
    • /
    • 2014
  • Experimental investigation on the structural behavior of steel fiber-reinforced ultra high performance concrete (UHPC) beams subjected to torsion are presented. Six tests carried out on square beams under torsional moment are presented. The experimental parameters were the volume fraction of the fibers and closed-stirrup ratio. The volume fraction of the fibers was 1.0% and 2.0%. The closed-stirrup ratio was 0, 0.35%, and 0.70%. The test results indicated that ultimate torsional strength increased with increasing fiber volume, and that ultimate torsional strength also increased with increasing the closed-stirrup ratio. In addition, predictive equations for evaluating the ultimate torsional strength of UHPC beams were proposed. The comparison between computed values and the experimentally observed values was shown to validate the proposed analytical equations. It was found that predictions by using proposed equation provides good agreement with test results of UHPC beams.

Experimental Study on Global Buckling of Singly Symmetric FRP Members (일축대칭 FRP 부재의 전체좌굴에 관한 실험적 연구)

  • Lee, Seungsik
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.26 no.1A
    • /
    • pp.99-106
    • /
    • 2006
  • Due to single symmetry of cross section, T-shaped members are likely to buckle in a flexural-torsional mode when they are subjected to axial compression. Therefore, the flexural-torsional buckling can be regarded as a governing mode of global buckling. An experimental program has been carried out to investigate the flexural-torsional buckling behavior of pultruded T-shaped members. Two types of pultruded members were tested in the experiment, and they were made of either E-glass/vinylester or E-glass/polyester. Lay-up and thickness of reinforcing layers, volume fractions of each constituents in layers, mechanical properties were experimentally determined. Two sets of knife edge fixure were used to simulate simple support condition for flexure and twisting, and the lateral displacements and the angle of twist were measured using three potentiometers. Every specimen buckled in a flexural-torsional mode, and most of the specimens showed post-buckling strength.

Torsional moment of orthodontic wires (교정용 와이어의 비틀림 모멘트)

  • Choy, Kwangchul;Kim, Kyung-Ho;Park, Young-Chel;Kang, Chang-Soo
    • The korean journal of orthodontics
    • /
    • v.30 no.4 s.81
    • /
    • pp.467-473
    • /
    • 2000
  • As a rectangular wire Is inserted into edgewise brackets the wire exerts a force system three-dimensionally. The force system may include bending force in first and second orders and a torsional force in third order Analytical and experimental studies on bending force have been Introduced, but information about torsion is still lack. The purpose of this study was to estimate the torsional moment in the force system of rectangular arch wires through theoretical and experimental studies. Wires most frequently used for third order control were selected as study materials. Cross sections of 0.016x0.022, 0.017x0.025, 0.019x0.025 inch rectangular wires in foot different materials such as stainless steel(Ormco), TMA(Ormco), NiTi(Ormco), and braided stainless steel (DentaFlex, Dentaurum) were used. The torque/twist rate of each test material was calculated using the torsion formula. Torque/twist rate, yield torsional moment, and ultimate torsional moment were measured with a torque gauge. The torsion formula assesses that the torque/twist rate (T/$\theta$) is proportional to the characteristics of material (G) and cross section (J), and is inversely proportional to the length of wire (L). Most experimental results corresponded with the formula. The relative stiffness was calculated for reference to a logical sequence of wire changes.

  • PDF

The influence of intentional mobilization of implant fixtures before osseointegration (골유착전 임플란트 고정체의 의원성 동요가 골결합에 미치는 영향)

  • Cho, Jin-Hyun;Jo, Kwang-Heon;Cho, Sung-Am;Lee, Kyu-Bok;Lee, Cheong-Hee
    • The Journal of Korean Academy of Prosthodontics
    • /
    • v.50 no.3
    • /
    • pp.149-155
    • /
    • 2012
  • Purpose: The purpose of this study was to investigate the influence of mobilization on bone-implant interface prior to osseointegration of fixtures. Materials and methods: The experimental implants (3.75 mm in diameter, 4.0 mm in length) were made of commercially pure (Grade IV) titanium, and were treated with RBM ($MegaGen^{(R)}$: Ca-P). The 80 implants (two in each tibia) were inserted into the monocortical tibias of 20 rabbits which each weighed more than 3.5 kg (Female, New Zealand White). According to the removal torque interval, the groups were divided into 10 groups, Group I (6 wks), Group II (4 days+6 wks), Group III (4 days+1 wk+6 wks), Group IV (1 wk+6 wks), Group V (1 wk+1 wk+6 wks), Group VI (2 wks+6 wks), Group VII (2 wks+ 1 wk+6 wk), Group VIII (3 wks+6 wks), Group IX (3 wks+1 wk+6 wks) and Group X (10 wks). The control groups were Group I and X, the removal torque was measured at 6 wks and 10 wks with a digital torque gauge (Mark-10, USA). In the experimental groups, the removal torque was given once or twice before the final removal torque and the value was measured each time. After which, the implants were put back where they had been except the control groups. All the experimental groups were given a final healing time (6 wks) before the final removal torque test, in which values were compared with the control groups and the 1st and/or 2nd removal torque values in each experimental group. Results: In the final removal torque tests, the removal torque value of Group X (10 wks) was higher than that of Group I (6 wks) in the control groups but not statistically different. There were no significant differences between the experimental groups and control groups (P>.05). In the first removal torque comparison, the experimental groups (4 days or 1 wk) values were significantly lower than the other experimental groups (2 wks or 3 wks). In the comparison of each experimental group according to healing time, the final removal torque value was significantly higher than the 1st torque test value. Conclusion: Once or twice mobilization of fixture prior to osseointegration did not deter the final bone to implant osseointegration, if sufficient healing time was given.

Investigation of osseointegration according to the healing time after having iatrogenic mobility of implant fixtures (임플란트 고정체의 인위적 비틀림 후 시간 경과에 따른 골재유착 반응에 관한 연구)

  • Hwang, Yun-Jin;Cho, Jin-Hyun;Lee, Cheong-Hee
    • The Journal of Korean Academy of Prosthodontics
    • /
    • v.48 no.4
    • /
    • pp.308-314
    • /
    • 2010
  • Purpose: The purpose of this study is to analyze the change in re-osseointegration over time and bone reaction at the interface between implant fixture and the surface of the bone, after destroying re-osseointegration by distorting the bone-implant interface artificially. Materials and methods: Experimental implant fixtures (cp titanium, ${\phi}3.75\;mm{\times}4\;mm$) which didn't have surface treatment were produced. Two or three fixtures were implanted on both tibias of twelve female rabbits (New Zealand white, more than 3.5 kg). Then after six weeks, removal torque (RT) was measured and the results were recorded as the first measurement values. The fixtures were submerged again to get reosseointegration between the bone and fixture. To identify the change in re-osseointegration of submerged fixtures over time, six groups had the healing time for four days (group I), one week (group II), two weeks (group III), three weeks (group IV), four weeks (group V) and five weeks (group VI), and then the secondary removal torque was measured for each group. To identify the bone formation under fluorescent light, tetracycline (15 mg/kg, IM) were treated on the rabbits of each group. After the second measurement, the rabbits were sacrificed, and 16 slides were made, two or three for each group. The slides were observed under the fluorescent light with light microscope. To find out the change in the secondary removal torque over the primary removal torque in progress of time, the averages of the increase rate of the primary and secondary torque removal force were calculated. Then, to find out if there were any critical differences between the primary removal torque and the secondary removal torque in each group and among the groups, the results were analyzed statistically by paired t- test, one-way ANOVA, and Duncan's Multiple Range Test. Results: In group I and II, secondary removal torque decreased, especially in group I. In group III, IV, V, and VI, secondary removal torque increased critically. Comparing the differences among the groups, the critical difference was shown between group I, II and group III, IV, V, VI. Mineralization at the interface between the bone and implant fixture was identified from the first week, and bone formation was shown more clearly from the second week. Conclusion: If the implant fixture remains unforced for a certain period of time after the fixture has had iatrogenic mobility, re-osseointegration occurs at the surface of the fixture, and for tibias of rabbits, higher re-osseointegration was obtained within two weeks.

Failure Modes of RC Beams with High Strength Reinforcement (고강도 비틀림보강철근을 사용한 철근콘크리트 보의 파괴모드)

  • Yoon, Seok-Kwang;Lee, Su-Chan;Lee, Do-Hyeong;Lee, Jung-Yoon
    • Journal of the Korea Concrete Institute
    • /
    • v.26 no.2
    • /
    • pp.143-150
    • /
    • 2014
  • To avoid abrupt torsional failure due to concrete crushing before yielding of torsional reinforcement and control the diagonal crack width, design codes specify the limitations on the yield strength of torsional reinforcement of RC members. In 2012, Korean Concrete Institute design code increased the allowable maximum yield strength of torsional reinforcement from 400 MPa to 500 MPa based on the analytical and experimental research results. Although there are many studies regarding the shear behavior of RC members with high strength stirrups, limited studies of the RC members regarding the yield strength of torsional reinforcement are available. In this study, twelve RC beams having different yield strength of torsional reinforcement and compressive strength of concrete were tested. The experimental test results indicated that the torsional failure modes of RC beams were influenced by the yield strength of torsional reinforcement and the compressive strength of concrete. The test beams with normal strength torsional reinforcement showed torsional tension failure, while the test beams with high strength torsional reinforcement greater than 480 MPa showed torsional compression failure. Therefore, additional analytical and experimental works on the RC members subjected to torsion, especially the beams with high strength torsional reinforcement, are needed to find an allowable maximum yield strength of torsional reinforcement.